US2313710A

US2313710A - Screw driver

Info

Publication number: US2313710A
Application number: US348392A
Authority: US
Inventors: James H Gemmell
Original assignee: Individual
Current assignee: Individual
Priority date: 1940-07-30
Filing date: 1940-07-30
Publication date: 1943-03-09
Anticipated expiration: 1960-03-09

Description

AlVlarh-Q, :1943.

#16 y l-1131; E;

J.H. GEMMELL. SCREWV DRIVER vFiled July 3o. 1940 ATTORNEY Patented Mar. 9, 1943 UNITED STATES PATENT OFFICE SCREW DRIVER James H. Gemmell, Oakland, Calif.

Application July 30, 1940, Serial No. 348,392

3 Claims. `(Cl. 145-50) The present invention relates to screw drivers of the screw holding type and is concerned more particularly with the provision of an improved screw driver of this type which is economical to manufacture and assemble, and is constructed to hold a screw effectively.

It is a general object of the invention, therefore, to provide an improved screw holding screw driver. Another object of the invention is to provide an improved screw holding screw driver which is constructed to facilitate economical production and assembly.

Another object of the invention is to provide an improved screw holding screw driver which is provided with screw engaging surfaces of a novel construction to enable maximum surface to surface contact between the driver bit` and the screw slot.

l Other objects and advantages of the invention will be apparent from the `following description of a preferred embodiment thereof as illustrated in the accompanying drawing, in which:

Figure l is an elevational view of a screw driver constructed in accordance with the instant invention;

Figure 2 is an enlarged view of the screw driver with `the handle shown in section;

Figure 3 is an enlarged view similar to Figure 2 but taken at right angles thereto;

Figure 4 is an enlarged detail view showing the screw driver in screw holding relation with `a screw; y

Figure 5 is a transverse sectional view taken in a plane indicated by the line 5-5 in Figure 3;

Figure 6 is a transverse sectional view taken in a plane indicated by the line 6-6 in Figure 3;

Figure 7 is a transverse sectional view taken in a plane indicated by the line I--l in Figure 3;

Figure 8 is a fragmentary sectional view illustratng a modified form of construction; and

Figure 9 is a transverse sectonal view taken in a plane indicated by the line 9 9 in Figure 8.`

Referring to Figure l, the screw driver includes a tubular handle I0 in which a blade assembly including a head I I and a release rod I2 are mounted for sliding movement.

The blade assembly comprises opposed similar bit sections I6 (Figs. 1-3) which are blanked and formed from sheet metal stock. Each bit section I6 includes an semi-cylindrical shank portion I1 adapted to engage a reduced portion I8 of the release rod I2 and fit closely within the tubular handle I IJ. Each semi-cylindrical portion I'I is provided with a circumferentially extending locking ear I9 which extends into the mating recess 2l of the cooperating bit section and which is formed inwardly from the curvature of the semicylindrical portion to engage in a locking groove 22 in the rod. The groove 22 in the rod is formed between portions I8 of the rod of the same diameter for engagement with the semi-cylindrical portion I'I of the bit section.

From the semi-cylindrical portion I1 thereof, each bit section converges radially inwardly to form a tapered portion 23 which has inner cam edges 24- for cooperation with retaining and spreading pin 26 suitably secured as by riveting in diametric position in the tubular handle. The tapered portions 23 of the opposite bit sections terminate in heads 21 which flare outwardly toa greater diameter` and then taper down to theV screw engaging ends.

The head portions 21 of the respective bit sections terminate in screw slot engaging ends 28 of special construction. The inner surfaces of ends 28 are preferably flat for flush engagement in the released position of the tool as seen in Figure 2. The outer surfaces of ends 28 are formed to provide a thinner section 29 in the bit closely adjacent but spaced from the end edge. While it is preferred to form the surface 29 with a radius, it may be formed in any other suitable manner to provide a thinner section at a point spaced from the end of the screw engaging portion for cooperation with the walls of the screw slot when the bit sections "are engaged therewith. This condition is shown in Figure 4 where the substantial area of contact between the bit sections and the screw slot walls is clearly evident.

As shown, the release rod I2 is provided with an extension 3|, which in the released position of the screw driver' engages pin 26, as shown in Figures 2 and 3 to provide a stop for the movement of the head of the screw driver in one direction relative to the handle. Movement in the other direction is limited by the engagement of head portions 2l with the end of the tube.

To assemble the bit sections on the head I2, theyare placed on the rod by substantially radial movement relative thereto with their bent ears I9 engaging in the groove 22 so that their semicylindrical portions II t the reduced portion I8 of the rod snugly. The rod and head assem- I bly is then slid into the tube so that the bit sections are held on the rod by the tube which prevents the ears I9 from moving out of the groove radial movement out of engagement therewith. The pin 26 is then inserted and fastened as by riveting to complete the assembly.

Figure 4 illustrates the engagement of the screw driver with a screw, which engagement is effected merely by pushing the screw Sii onto the bit sections, and continuing the pushing until the blade and release rod assembly telescopes inwardly with respect to the tubes. During the telescoping movement engagement of pin 26 with the inner cam edges 2i of the bit sections causes expanding thereof so that the screw engaging ends are forced outwardly into engagement with the opposite side walls of the screw slot 3l. By providing thicker end edges for the screw engaging portions of the bit sections, a substantially surface-to-surface engagement can be established between the walls of the screw slot and the outer side faces of the bit sections, as seen in Figure 4l, where the curvature provided is slightly exaggerated. This enables a substantially greater frictional holding force to be exerted on the screw. Obviously where a screw driver is designed for a particular size of screw, the angularity of the outer surface of the bit section may be controlled to maintain a substantially glush engagement between the bit sections and the walls of the screw slots when lthe bit sections are flexed during expansion thereof while being engaged in a screw.

igures 8 and 9 illustrate a modified form of construction which is generally similar to that described in connection with Figures l to 7, but varies therefrom in certain particulars. In the form shown in Figures 8 and 9, the bit sections liia are secured on the release rod l2a independently of the tubular handle Eta and the locking ears 19a not only serve to lock the bits against endwise movement on the rod but also against radial movement relative thereto. As seen most clearly in Figure 9, this is accomplished by eX- tending the locking ear ma to circumferential length of slightly more than 90, so that the spacing between the end of ear lila and the opposite side edge of the bit is less than diameter'V of the reduced portion 22a of the rod E2G. The rod 2a is provided with a tapered end portion ,3io which extends downwardly from the lower reduced portion ltd In assembly, the bit sections !ia are placed in mating engagement and Vthen slid endwise over the tapered end portions i l. A screw driver of the screw-engaging type @comprising a tubular handle and a blade assembly mounted for telescoping movement within the handle, said blade assembly including a pair of opposite bit sections formed to provide complemental inter-engaging portions to facilitate assembly in the desired relative positions and a rod for engagement by said portions, circumferential ears and opposed recesses on said bit sections, said ears having their ends formed i inwardly from their general curvature, recess means on said rod for engagement by said inwardly formed ends, and cam means carried by said handle and extending between said bit sections to engage cam portions thereof upon movement oi said blade assembly within said handle and cause expansion of said bit sections into holding engagement with a screw.

2. A screw driver of the screw-engaging type comprising a tubular handle and a blade assembly mounted for telescoping movement within the handle, said blade assembly including a pair of opposite bit sections formed to provide complemental inter-engaging portions to facilitate assembly in the desired relative positions and a rod r Vfor engagement by said portions, circumferential ears and opposed recesses on said bit sections, said ears having their ends formed inwardly from their general curvature, recess means on said rod for engagement by said inwardly formed ends, said ears serving rto prevent both endwise and radial movement of said Vbit sections, and cam means carried by said handle and extending between said bit sections to engage cam portions thereof upon movement of said blade assembly within said handle and cause expansion of said bit sections into `holding engagement with a screw. i

3. A screw driver of the screw-engaging type comprising a tubular handle and a blade assembly mounted for telescoping movement within the handle, said blade assembly including a pair of opposite bit sections formed to provide screw engaging portions and with complemental interengaging portions to facilitate assembly in the desired relative positions, and a Yrod for engagement by said portions, circumferential ears and opposed recesses 'onsaid bit sections, said ears having their ends formed inwardly from their general curvature, recess means on said rod for engagement by said inwardly formed ends, and

means operable in response to relative endwise movement of said handle andY said blade assembly for spreading said screw-engaging portions into holding engagement with a screw.

JAMES H. GEMMELL.